Map limits don't change drastically in flight but they do change; in my last flight there were times during cruise when MCP was 23+" and other times when it was 21". More relevantly though, Vne changed dramatically, from 130 kts at departure down to 103 kts when going over a mountain at high temperatures. I would absolutely pay extra for something that makes this easier to manage. I may even write my own Android app to show the current map/Vne limits, though I don't know how to feed it OAT so that may have to be selected onscreen (simple slider).
The ideal solution would be for the Garmin PFD to be programmed to change its yellow/red IAS arc dynamically based on conditions, because it does know OAT and altitude. (Pilot would have to remember the 2200 lb thing.)